For a geophone, the preamp, shielding, and signal conditioning is at least as important as the sensor, and (IMHO) the hardest to do well. A preamp to operate near DC, with low input impedance ...

At CES 2025, two years after Qi2 was first introduced, the first update to the standard was released. It brings “Qi2 Ready,” as well as new support for chargers that have a moving coil.